Turtle rescues happen every year in late fall in the Northeast, but for reasons not yet known what's happening this year is "epic," said one of the nearly two dozen volunteers passing boxes of turtles like a bucket brigade.

"Statistically, I feel like we are out on Pluto," said Tony LaCasse, spokesman for the New England Aquarium's marine-animal hospital in Quincy, Mass., who fears the number of cold-stunned turtles could quadruple.

"We've been rescuing sea turtles for 25 years, and we are just absolutely shocked," LaCasse said.

Among possible explanation for the huge spike in turtle rescues – the record of 242 in 2012 has been eclipsed already this year by more than 400 rescues – is that the number of highly endangeredKemp's ridleys has been increasing slightly in recent years.

So when more of them turned up for their normal summer feast on crabs in Cape Cod Bay, more were trapped there when water temperatures began to drop in September.

The bay is shaped like a bucket, and turtles have to swim 25 miles to the north to get over the lip of the bucket and escape to warmer waters to the south.

"They slowly get hypothermic over six to eight weeks," LaCasse said. "Their body temperature goes from about 70 at Labor Day to 60 Oct. 1 and near 50 by mid-November. What happens in November is we get big north winds and wave activity that washes them up on beaches of Outer Cape Cod."

Many of the rescues have been done by volunteers with the Massachusetts Audubon Sanctuary at Wellfleet Bay.

"When the turtles wash up on the beach, they look dead," said Audubon spokeswoman Jeanette Kerr.

The Coast Guard HC-144, a twin-propeller plane, landed just before 5 p.m.

Co-pilot Gary Kuehn said the flight was an hour longer than planned because of stormy weather.

"I heard the turtles flop around a little bit," said Ross Ruddell, a Coast Guard spokesman.

But the cargo wasn't that unusual, said load master Trey Edenfield, who was part of flights rescuing pelicans and a dolphin from the Gulf of Mexico oil spill in 2010.

The nearly two dozen veterinarian, biologists, drivers and government officials, coordinated by the Florida Fish and Wildlife Conservation Commission, huddled in the rain waiting. As soon as the plane's engines shut down, they went to work, counting out turtle numbers as boxes were loaded into van.

Within 10 minutes, the first van left for a drive to an aquarium in the Keys. In all, seven aquariums from South to North Florida took some of the reptiles for rehabilitation.SeaWorld took 72 of them.

Turtles also have gone to other states recently, including 50 taken to North Carolina, 31 to Georgia, 20 to South Carolina and 14 to Pennsylvania.

The Florida turtles are likely to be released into the Gulf of Mexico, which is probably the survivors' birth waters. More than 90 percent of nesting occurs along beaches of the state of Tamaulipas, Mexico.

As the pace of unloading eased, Edenfield got permission to hold one of the turtles for the first time. Like the rest, it looked sleepy and was about the size of a dinner plate. But for a few seconds, its flippers went to work, stroking through the warm air of Florida.